The present invention relates to an apparatus for removing and/or recovering ink, a printing machine including such an apparatus, and a method for supplying and/or recovering ink, and more particularly, to such an apparatus, machine and method which can remove and/or recover ink remaining in ink delivery tubings connecting an ink reservoir to an ink supply source.
Conventionally, when a printing machine prints a sheet of paper, such as a corrugated board with flexographic ink, it is common to press a printing die having ink applied thereon against the surface of the sheet. These printing machines, such as disclosed in Japanese Utility Model publication H03-14367, usually include a pair of rollers, one of which supports the printing die on the outer surface thereof, an ink reservoir formed between said roller and another roller engaging therewith, an ink supply source, and at least one of ink delivery tubings each connecting the ink reservoir to the ink supply source to enable fluid communication therebetween, so that the ink supplied from the ink supply source to the ink reservoir via the ink delivery tubings and accumulated in the ink reservoir is transferred to the printing die and used for printing.
The remaining ink in the ink reservoir is recovered therefrom and returned back to the ink supply source via the ink delivery tubings, after the printing operation has finished. However, even after the ink remaining in the ink reservoir has been completely recovered from the ink reservoir and returned back to the ink supply source via the ink delivery tubings, excess ink still remains on the surfaces of the pair of rollers and the ink reservoir, and on the inner surfaces of the ink delivery tubings, therefore it is important to remove or rinse out such remaining ink as quickly as possible before successive printing operation which uses ink of anothor color is conducted.
There are several technical problems in such printing machines, especially due to the ink remaining in the ink delivery tubings.
The first problem is that the ink used in the previous printing operation and still remaining in the ink delivery tubings will be mixed with ink of a new, different color upon the start of a successive printing operation, thereby the printed color does not precisely match the color of the new ink. A printing color is quite often changed even in one day, since small lot productions are recently required. Japanese Utility Model Laid-open publication S63-77737 discloses a printing machine wherein excess ink remaining in the ink reservoir can be recovered and sent back to the ink supply source via the ink delivery tubings by using an air ejector. Although it would be possible to remove ink remaining in the ink reservoir according to this apparatus, it is still difficult to remove ink remaining in the ink delivery tubings.
The second problem is that it is difficult to efficiently remove ink remaining in the ink delivery tubings such as ink supply tubings or ink recovery tubings. Japanese patent 2,954,895 discloses an apparatus for recovering flexographic ink remaining on the surface of a pair of rollers wherein the remaining ink is diluted, and then recovered via the ink delivery tubings after supplying a sufficient amount of diluting liquid to the ink reservoir. It would be possible, according to this apparatus, to remove some of the ink remaining in the ink delivery tubings by diluted ink flowing through the ink delivery tubings.
However, it is difficult to completely remove all of the ink from the ink delivery tubings, therefore the ink delivery tubings must be rinsed out again using a large amount of rinsing water.
The third problem is that it is difficult to recover ink from the ink delivery tubings such as ink supply tubings and ink recovery tubings, so that the recovered ink can be reused thereafter. Although the excess ink remaining in the ink delivery tubings could be removed by rinsing the ink supply tubings and ink recovery tubings, the recovered ink will be diluted so much that it cannot be reused for printing. If the ink can be recovered while still in its reusable form, the loss of the ink will be reduced.
According to the prior art, the excess ink remaining in the ink reservoir and/or on the surface of the pair of rollers is recovered, however, excess ink remaining in the ink delivery tubings has to be rinsed out with a large amount of rinsing water, thus causing significant amount of loss of ink and waste water, whereby harm to the environment is caused.
As to the amount of loss of ink and of waste water, assuming a flexographic printing machine for corrugated boards of 2,500 mm in width among others, the machine including a conventional ink recovery system, the amount of flexographic ink wasted upon color change, i.e. remaining in the ink supply tubings, ink recovery tubings, and on the ink pan which should be rinsed out by rinsing water, is about 150 grams for each color thereof (assuming that flexographic ink remaining in the ink reservoir is recovered by the ink recovery system thereof.). The amount of rinsing water which is consumed for rinsing out such flexographic ink is about 50 liters. Therefore, when a color change is required 30 times a day, each color of ink wasted in a day will be 150 grams times 30, that is 4,500 grams, for each printing machines. Similarly, waste water required for rinsing flexographic ink out from the ink supply tubings, ink recovery tubings, and the ink pan, will be 50 liters times 30, that is 1,500 liters in a day. Thus it can be seen from the above that, conventional flexographic printing machine has been required to waste large amounts of flexographic ink and rinsing water.
Thus, one object of the present invention is to provide an apparatus for removing and/or recovering ink, a printing machine including such an apparatus, and a method for supplying and/or recovering ink, which can remove ink remaining in ink delivery tubings connecting an ink reservoir to an ink supply source, thereby preventing a change of printing color due to the mixture of a previous ink and new ink.
Another object of the present invention is to provide an apparatus for removing and/or recovering ink, a printing machine including such an apparatus, and a method for supplying and/or recovering ink, which can quickly remove or rinse out the ink remaining in ink delivery tubings connecting an ink reservoir to an ink supply source.
Still another object of the present invention is to provide an apparatus for removing and/or recovering ink, a printing machine including such an apparatus, and a method for supplying and/or recovering ink, which can recover the ink while it is still in its reusable form, which remains in ink delivery tubings connected between an ink reservoir and an ink supply source.